Vps26² mutant photoreceptor cells exhibit a progressive loss of ERG amplitudes compared to controls. Upon rearing these flies in the dark, Vps26² mutants exhibit nearly normal ERG responses and the ERG amplitude and on- and off-transients in Vps26² mutant photoreceptor cells are slightly reduced when compared to controls.

In a 12-hour light/dark cycle, Vps26² flies show a loss of on- and off-transients, indicating a loss of synaptic transmission. They also exhibit a reduced depolarisation by 2 day, and a progressive loss of the ERG amplitude witih age. At day 21, the light-induced photoreceptor cell depolarisation in Vps26² mutant photoreceptor cells is almost completely absent. Three-week-old dark/dark-reared Vps26² mutants exhibit nearly normal ERG responses, similar to newly eclosed flies. The photoreceptor cell morphology of Vps26² mutants is severely affected in flies kept in light/dark conditions for 21 days.